Chapter 9 - Axial Skeleton Osteology & Arthrology

Two main functions of SI joint:

stress relief within the pelvic ring, provides a stable means for load transfer between axial skeleton and lower limbs

The ____________ spine permits a relatively constant amount of lateral flexion. This kinematic feature reflects the general frontal plane orientation of the apophyseal joints combined with the stabilizing effect of the ribs.

thoracic

With the exception of the sacroiliac joints, the __________ region as a whole is the most mechanically stable portion of the vertebral column.

thoracic

The ____________ spine, from a cranial-to-caudal direction, permits increasing amounts of flexion and extension at the expense of axial rotation.

thoracolumbar

The lumbar spine possesses a 55-70 degree arc of motion in the sagittal plane (flexion / extension). The predominance of sagittal plane motion is largely a result of the prevailing sagittal plane orientation of the facet surfaces of the lumbar __________ joints.

apophyseal

much of the characteristic motion allowed within each region of the vertebral column is dictated by the spatial orientation of ____________ joints.

apophyseal

Horizontal facet surfaces favor _____________, while vertical facet joint surfaces (in either saggittal or frontal plane) block axial rotation.

axial rotation

The primary motion at the atlanto-axial joint is

axial rotation

Three key points of intradiscal pressure studies (from graph in book)

(1) disc pressures are large when one holds a load in front of the body, especially when bending forward; (2) lifting a load with knees flexed places less pressure on the lumbar disc than does lifting a load with the knees straight ; and (3) sitting in a forward-slouched position produces greater disc pressure than sitting erect.

Mechanical or structural factors that may lead to a herniated nucleus pulposus in the lumbar spine:

1. Preexisting disc degeneration with radial fissures, cracks, or tears in the posterior annulus that allow a path for the flow of nuclear material 2. Sufficiently hydrated nucleus capable of exerting high intradiscal pressure 3. Inability of the posterior annulus to resist pressure from the migrating nucleus 4. Sustained or repetitive loading applied over a flexed and rotated spin

What two forces comprise the nutation torque about the SI joint?

1. downward force of gravity resulting from body weight that passes through the lumbar vertabrae 2. upward directed compression force from femoral heads pushing up in acetabulum

The kinematics of thoracolumbar lateral flexion are the sum of _____ degrees of thoracic lateral flexion and _____ degrees of lumbar lateral flexion

25, 20

The lumbar spine can move in _____ degrees of freedom

3 (flex.ext, axial rotation, lateral flexion)

Normal degree of cervical lordosis?

30-35

Normal degree of thoracic kyphosis?

40

Normal degree of lumbar lordosis?

45

In the lumbar region, collagen rings are oriented, on average, about ______ degrees from the vertical, with fibers of adjacent layers traveling in opposite directions.This structural arrangement offers significant resistance against intervertebral distraction (vertical separation), shear (sliding), and torsion (twisting

65

What two ligaments resist the natural anterior shearing force produced at the L5-S1 junction?

Anterior longitudinal and iliolumbar ligaments

Retraction extends the lower cervical spine and ________ the upper craniocervical region.

Flexes

The cervical spine can protract or retract in a greater ROM?

Protract

At the atlanto-occitial joint, the convex occipital condyles roll backward and slide forward in extension

TRUE

True or false: nutation torque increases stability at the SI joints

TRUE

true or false? the convex occipital condyles roll backward and slide forward in extension and forward in flexion while sliding backward within the concave superior articular facets of the atlas

TRUE

Increasing the degree of lumbar lordosis enlarges the sacrohorizontal angle, which in effect ______________ the anterior shear at the L5-S1 junction a. increases b. decreases

a. increases

Clinically referred to as "check ligaments," the _______ ligaments are respected for their ability to resist, or check, axial rotation of the head-and-atlas relative to the dens.

alar

Full extension tends to deform the nucleus pulposus in an ______________ direction.

anterior

What two ligaments reinforce the anterior side of the SI joint?

anterior sacroiliac & iliolumbar ligaments

The relative frontal plane bias of the apophyseal joints of the L5-S1 junction provides important restraint to what potentially damaging force?

anterior shear force

The _________ spine permits relatively large amounts of motion in all three planes.

cervical

In axial rotation at the lumbar spine, the apophyseal joints located _________________ to the side of rotation compress/approximate, blocking further movement.

contralateral

Which region of the vertebral column is the most mobile?

craniocervical

All of the following ligaments become taut in flexion EXCEPT: a. posterior longitudinal ligament b. interspinous ligaments c. ligamentum flavum d. anterior longitudinal ligament e. supraspinous ligament

d. anterior longitudinal ligament

When material from the nucleus pulposus impinges against the spinal cord or nerve roots, a painful impairment develops called _______________________

disc herniation

What muscles reinforce / stabilize the SI joint?

erector spinae, lumbar multifudi, abdominal muscles, hip extensors, latissimus dorsi, iliopsoas

Protraction of the head flexes the lower/mid cervical spine and ____________ the upper craniocervical region.

extends

The approximation of the apophyseal joints limits the extremes of what movement?

extension

Lumbar ________ increases the diameter of the intervertebral foramen. a. flexion b. extension

flexion

The ligamentum nuchae and interspinous ligaments provide significant restraint to the extremes of ___________

flexion

What motions can occur at the atlantooccipital joint?

flexion and extension. Lateral flexion is slight. Axial rotation is severely restricted and not considered as the third degree of freedom

The ligamentum nuchae and interspinous ligaments provide significant restraint to the extremes of ___________, whereas the approximation of the apophyseal joints limits the extremes of ___________

flexion, extension

The near-sagittal plane orientation of middle and upper apophyseal joints within the lumbar region allows ample flexion and extension of the lower end of the vertebral column while simultaneously resisting ___________ plane rotation.

horizontal

The base of the sacrum is naturally inclined anteriorly and __________.

inferiorly

What type of joint contains an intervertebral disc, vertebral endplates, and adjacent vertebral bodies?

interbody joint

The pathomechanics of exaggerated lumbar ____________ often involve a hip flexion contracture with increased passive tension (tightness) in the hip flexor muscles

lordosis

The ___________ spine, in combination with flexion and extension of the hips, forms the primary pivot point for sagittal plane motion of the entire trunk.

lumbar

If a disc is herniated posteriorly, what type of exercises should you emphasize?

lumbar extension

The close packed position of the apophyseal joints is what?

neutral or slightly extended (this maximizes the area of contact within the apophyseal joints)

Given the natural 40 degree anterior tilted angle of the base of the sacrum, ones body weight created an anterior shear force and compressive force acting ___________ to the superior surface of the sacrum.

perpendicular

Name the components of the nucleus pulposus:

proteoglycans, type II collagen fibers, elastin fibers, and water (70%)

The outermost or peripheral layers of the annulus fibrosus consist primarily of type I and type II collagen. This arrangement provides circumferential ____________ and ____________ to the disc, as well as a means to bond the annulus to the anterior and posterior longitudinal ligaments and to the adjacent rim of the vertebral bodies and endplates.

strength, flexibility

In cervical rotation, at the apophyseal joints, the inferior facets slide posteriorly and slightly inferiorly on the same side as the rotation, and anteriorly and slightly superiorly on the side opposite the rotation

truth

The facet surfaces of most lumbar apophyseal joints are oriented nearly ____________, with a moderate/strong ___________ plane bias.

vertically, sagittal